Automotive vehicles, and particularly vehicles designed to transport goods by road, such as trucks, are generally driven by their rear axles, with a powertrain consisting of the engine and gearbox, mounted in the front section of the vehicle. The powertrain and the powered wheels are connected by a shaft, commonly called a driveshaft, that is connected on one side to the powertrain outlet, generally the gearbox, while on the other it is connected to the differential, in order to transmit power to the wheels.
For road cargo vehicles with two rear axles and more particularly, truck tractors with two rear axles, vehicles may have a 6×2 or 6×4 drivetrain configuration, meaning that only two of the six wheels of the vehicle are powered, generally the two wheels on the first rear axle, or the four wheels on the two rear axles. In some applications, vehicles configured for off-road purposes may also have an 8×4 drivetrain configuration or even a 6×6 or 8×8 drivetrain.
The use of at least two powered axles, as in a 6×4 configuration, may be desirable for legal reasons (in some countries, such as Brazil, a 6×4 drivetrain configuration is required for vehicles carrying high-limit cargoes), as well as for use-related aspects, like vehicles intended for off-road purposes such as on sugarcane plantations or mining operations
However, in order to save fuel and reduce tire wear when a vehicle is not loaded, it may be desirable to take an axle out of use. If the drivetrain configuration is a 6×2 configuration, for example, one of the rear axles (not powered) may be raised, thus lowering fuel consumption and tire wear through a technical solution that is already quite widely known, in which an airbag is used to raise the axle, thus making good use of the compressed air line in this type of vehicle.
However, this solution may not be used in vehicles with 6×4 or 8×4 drivetrain configurations, for example, because powered axles may not be raised, as power sent to the raised axle would be lost.
Nevertheless, there is a need to connect or disconnect the drivetrain for at least one axle on a vehicle, particularly a cargo vehicle such as a truck or truck tractor.
The state of the art encompasses some solutions that allow automatic or manual selection of a drivetrain for one or more axles. One known solution consists of connecting or disconnecting the central differential geartrain that powers the axle. However, this solution may not be used for 6×4 or 8×4 drivetrain configurations as no central differential is generally used, with driving power transmitted from one differential geartrain to another sequentially through a driveshaft.
Other more elaborate solutions, such as those disclosed in Arai documents US 2012/0260758 that constitute the state of the art, deploy more complex resources such as clutchplates and electronic controls. Such solutions are complex and expensive, and may not even work properly for very high torques such as those required for cargo vehicles whose engine torques may easily exceed 1500 Nm and might even reach 3000 Nm.
Consequently, the need persists for a simple technical solution that can be used—with no need for electronic controls—for connecting or disconnecting the drivetrain on the axle of a vehicle, particularly a road cargo vehicle with a 6×4, 8×4 or similar drivetrain configuration. This invention is intended to remove these inconvenient aspects of the state of the art, among others.